Topic/git status

Here's an attempt to implement the git_status. This will also change the calls in the worktree module in macgitver/libMacGitverModules (seperate PR follows).

- [ ] implementation of the repo status 
- [ ] implementation of the submodule status

@scunz: `git_status_foreach` and `git_status_foreach_ex` are deprecated. Any idea how to get the files different.